1. Field of the Invention
This invention relates to a method and apparatus for forming underground solidification structures such as soft ground reinforcing structures, underground cutoff walls and building foundations.
2. Description of the Related Art
In one of the prior art methods for reinforcing soft ground, a ground solidification material spouting tube was driven into the underground while imparting rotation thereto and solidification material was spouted through the tube into the underground to thereby solidify the soil and earth in the underground. However, such a prior art device had the disadvantage that, since the soil and gravel displaced from a selected area in the underground where the solidification material was spouted were mingled with the solidification material, the area could not be always reinforced with a calculated uniform strength which makes it difficult to provide an optional or desired strength to the underground area. Furthermore, since the solidification material is spouted through the jet nozzle at the leading or lower end of the spouting tube while the tube is rotating so that the operator cannot monitor which direction the nozzle is directed to, the solidification material is randomly spouted into the underground and mingles with the surrounding soil. Thus, the solidification structure to be formed in the underground was limited to a column- or sheet-like configuration. In addition, since the swivel joint through which rotational movement from an external driving device was transmitted to the spouting tube was subjected to limitation in design, spouting tubes having a plurality of liquid feed hoses such as three- and fourfold-spouting tubes could not be employed.